JPH01107219A - Optical fiber connecting structure of optical circuit substrate - Google Patents

Abstract

PURPOSE:To minimize the dispersion and loss of the light between an optical fiber and light guide by constituting the title structure in such a manner that the optical fiber can be fixed to the light guide in tight contact therewith. CONSTITUTION:This structure is constituted to connect the optical fiber 1 to a substrate 2 by using a V-groove 3 for guiding the optical fiber 1 and the 2nd groove 4 having perpendicular side faces which constitute incident faces for light. The optical fiber 1 can, therefore, be brought into tight contact with the light guide 6 and the light can be directly projected thereto. The dispersion and loss of the light in the juncture are thereby extremely minimized and the high coupling efficiency is obtd. Since the optical fiber 1 is guided by the V- groove 3, the assembly of the optical fiber 1 to the substrate 2 is easily and inexpensively executed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an optical integrated circuit, and more particularly to a structure for connecting an optical fiber to an optical circuit board.

``Prior Art J'' In an optical integrated circuit, it is necessary to couple an optical fiber to an integrated circuit board and to efficiently exchange optical information between the optical waveguide on the board and the optical fiber, that is, input and output light. The substrate is made of glass material or lithium niobate (LiNb).
o3) Crystal materials are often used, and thin film waveguides made of titanium (Ti) diffusion layers are mainly used as optical waveguides.

As shown in FIG. 9 and FIG. 1O, a conventional optical fiber connection structure for an optical circuit board includes forming a groove 31 in the substrate 2, aligning the optical fiber 1 along the groove 31, and fixing it with an ultraviolet curing resin. There is one in which the tip of the optical fiber 1 faces the optical waveguide 6 starting from the tip 32 of the fiber optic 31 and the light is directly input thereto.

However, since the substrate 2 is generally made of a highly brittle and difficult-to-cut material, it is generally difficult to process the grooves 31, and the grooves have been formed by grinding using a thin grindstone 33. For this reason, the shape of the end 32 of the spring 31 is determined by the radius of the grindstone 33, and when the optical fiber 1 is fixed in the groove 31, there is a gap S between the end surface of the optical fiber 1 and the optical waveguide 6.
There is a problem in that the dispersion and loss of light in this gap Sg becomes large. In addition, if the groove processing is performed by cutting without using the grindstone 33, minute chipping is likely to occur during groove processing, and the surface of the edge of the groove is rough, causing diffuse reflection of light and increasing optical loss. There was a problem.

"Problems to be Solved by the Invention" The present invention has been made to solve the above problems, and it enables the optical fiber to be closely fixed to the optical waveguide, thereby improving the connection between the optical fiber and the optical waveguide. An object of the present invention is to provide an optical fiber connection structure for an optical circuit board that can minimize optical dispersion and loss between the optical circuit boards.

``Means for Solving Problems'' Therefore, in the present invention, a 7-shaped groove having a V-shaped cross section,
A second layer is formed on the surface of the substrate, and is located at the tip of the 7-shaped groove and has a vertical side surface that is substantially orthogonal to the traveling direction line of the 7-shaped groove, and the side circumferential surface of the optical fiber is aligned along the 7-shaped groove. There is provided an optical fiber connection structure for an optical circuit board, characterized in that the optical fibers are arranged together and fixed to the board so that the tip end surface of the optical fiber abuts the vertical side surface of the second groove.

"Operation" According to the above configuration, the optical fiber connection portion is composed of two grooves. By arranging and fixing the optical fiber along the V-shaped groove, which is the first groove, the optical fiber can be accurately positioned on the optical circuit board. Since the second groove is formed perpendicular to the figure 7 groove, the tip end surface of the optical fiber can be brought into contact with the vertical side surface of the second groove. If the optical waveguide is formed on the substrate so as to start from the vertical TPL side surface of the second groove, the tip of the optical fiber can be accurately fixed in close contact with the optical waveguide. Since the light incident surface of the optical waveguide is a vertical side surface of the second groove, it can be polished to a precise plane with a mirror finish by grinding with the side surface of a disc-shaped grindstone. The light entrance surface is mirror-finished and there is no gap between the light entrance surface and the tip of the optical fiber, resulting in a connection structure with extremely low light dispersion and loss and high coupling efficiency.

"Embodiments" Examples of the present invention will be specifically described with reference to the drawings.

FIG. 1 is an exploded perspective view showing the connection points of optical fibers, and FIG. 2 is a longitudinal sectional view.

The optical circuit board 2 is made of lithium niobate (LiNbOs) crystal. In the substrate 2, a 7-shaped groove 3 having a V-shaped cross section is formed from one end of the substrate 2.
A flat groove 4, which is a second groove, is formed in a T-shape orthogonal to the groove. The depth of the flat groove 4 is formed slightly deeper than the 7-shaped groove 3,
The vertical side surface 5 facing the 7-shaped groove 3 is finished to be exactly perpendicular to the substrate surface and to be a precise flat surface without distortion. An optical waveguide 6 made of a titanium diffusion layer is formed on the surface of the substrate 2 along the extension line of the 7-shaped groove 3 in the traveling direction. The optical waveguide 6 is cut off by a vertical side surface 5 of the flat groove 4, and this vertical side surface 5 becomes the incident surface of light into the optical waveguide 6.

Optical fiber 1 is arranged with its side peripheral surface along 7-shaped groove 3, positioned so that the tip end surface of optical fiber 1 is in close contact with vertical side surface 5 of flat groove 4, and fixed on substrate 2 with ultraviolet curing resin. be done. At this time, the depth and shape of the 7-shaped groove 3 are formed so that the central core of the optical fiber 1 is accurately located on the end surface 6A of the leading waveguide 6. Therefore, the light transmitted through the core of the optical fiber 1 is directly incident on the end 6A of the optical waveguide 6. It becomes two.

A method of machining the 7-shaped groove 3 and the flat groove 4 will be explained. The processing procedure is to first form a 7-shaped groove 3 on a substrate 2 on which a guiding waveguide 6 has been formed in advance, and then to form a flat groove 4.

To form the 7-shaped groove 3, as shown in Fig. 3, a pyramidal tool 11 is used.
The cutting process is performed by The substrate 2, which is a workpiece, is a highly brittle and easily broken material such as niobium oxide (LiNbo 5). Pyramid tool 11 for processing this
is made of cemented carbide or diamond made by sintering ultrafine particles. The square tool 0.11 has the shape of a round bar with the tip sharpened into a square pyramid, and the pyramid part 12 forms the cutting edge.According to the shape indicated in -h, the tool rake angle of the pyramid tool 11 is Since the angle is negative, fragile parts can be cut with almost no chipping. Width and P! are formed on the substrate 2 using a pyramidal tool 11 in which the angle of the pyramidal part 12 (hereinafter referred to as the tip angle) is 60° and the diameter of the round bar part 13 is 5-. i is about 0.1am
Machining ■-shaped groove 3. Machining is performed by applying rotation and feed to the pyramidal tool 11 at the same time, similar to groove machining with an end mill.
Cutting is performed by the corner machining part 12, and the diameter is 0.
It is very difficult to make an end mill of 1 m+*, and it is easily broken, and cutting using an end mill breaks the substrate 2, making it impossible to process a groove.

FIG. 4 is a perspective view showing the ■-shaped groove 3 machined as described above. The V-shaped groove 3 is precisely formed to have a 7-shaped cross section in accordance with the shape of the pyramidal tool 11. Therefore, the optical fiber 1 having a circular cross section can be accurately positioned on the substrate 2, and the central axis of the optical fiber 1 can be aligned with jE.
It becomes easy to precisely match the position of the leading wave 1i'86.

Further, the shape of the tip end 14 of the machined V-shaped groove 3 is a small conical surface shape determined by the tip angle of the pyramidal tool 11 because the process is performed by rotating the pyramidal tool 11. The flat groove 4 is formed so as to eliminate the conical tip 14.

To form the flat grooves 4, precision grinding is performed using a thin disk-shaped grindstone 15, as shown in FIG.

- Since the curved surface shape of the tip 14 of the V-shaped groove 3 is small, the tip 14 can be removed using a thin disk-shaped grindstone 15 to form the vertical side surface 5 made of a flat surface.

The grindstone shaft 16 is set so as to be exactly parallel to the optical waveguide 6 on the surface of the substrate 2, and the disc-shaped grindstone 15 is sent in a direction perpendicular to the plane of the paper while rotating at high speed, creating a flat groove as shown in FIG. 4
is formed on the substrate 2. The vertical side surface 5 of the flat groove 4 is continuously ground by the side surface of the disk-shaped grindstone 15, so that it is finished into a mirror-like state without chipping.

As described above, according to the processing method of this embodiment, the square groove 3 for positioning the optical fiber 1 is efficiently processed by cutting, while the flat groove 4 forming the light incident surface (5° 6A) is The surface condition is improved by grinding.

In the embodiment described above, one optical fiber 1 is connected to the substrate 2, but as shown in FIG. It is also easy to form a structure in which a plurality of optical fibers 1 are connected.

In addition, by not making the flat groove 4 open to the side surface of the substrate 2, but by sending the disc-shaped grindstone 15 in the vertical direction, the groove is formed only in a short section of the substrate 2, as shown in FIG. 17 and its vertical side surface 18 can be used as the light entrance surface.

Furthermore, the grooves constituting the light incident surface are not limited to the flat grooves 4, but as shown in FIG. It is also possible to use the side surface 22 as a light incident surface to the optical waveguide 6.

Further, in the above embodiment, the flat groove 4 was formed so that the vertical side surface 5 of the flat groove 4 forming the light incident surface was perpendicular to the traveling direction line of the character fi 3 and the optical waveguide 6. Or slightly inclined laterally, the vertical side surface 5 and the optical waveguide 6
They may not be completely perpendicular to each other, as this may be preferable in order to prevent interference due to returned light at the light incidence surface 6A.

"Effects of the Invention" As explained above, the present invention has the above configuration, and uses a V-shaped groove for guiding an optical fiber and a second groove having a vertical side surface that forms a light incident surface to guide an optical fiber. Since it is connected to the substrate, the optical fiber can be brought into close contact with the optical waveguide and the light can be directly input, and the dispersion and loss of light at the connection part can be extremely minimized, making it possible to obtain high coupling efficiency. This has an excellent effect. Furthermore, since the optical fiber is guided by the V-shaped groove, it is extremely easy to assemble the optical fiber to the substrate, and it is possible to provide the optical fiber at a low cost.

[Brief explanation of the drawing]

1 to 8 show embodiments of the present invention, FIG. 1 is an exploded perspective view showing an optical fiber connection structure, FIG. 2 is a vertical sectional view, and FIG. 3 is a front view showing a V-groove processing method. 4 is a perspective view, FIG. 5 is a sectional view showing a method of forming a flat groove, FIG. 6 is a plan view showing the second embodiment, and FIG. 7 is a plan view showing the third embodiment. 8 are sectional views showing the processing method, FIG. 9 is an exploded perspective view showing a conventional connection structure, and FIG. 10 is a longitudinal sectional view. 191. optical fiber, 281. Board, 3,...
V-groove, 400. Hirazo, 501. Vertical side, 61
．． . Leading wave path. Figure 1 Figure 2 Figure 3 and Figure 4 [ Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 33 / Figure 10

Claims (1)

[Scope of Claims] A V-shaped groove having a V-shaped cross section, and a second groove located at the tip of the V-shaped groove and having a vertical side surface substantially perpendicular to the traveling direction line of the V-shaped groove. is formed on the substrate surface, and the side peripheral surface of the optical fiber is arranged along the V-shaped groove,
1. An optical fiber connection structure for an optical circuit board, characterized in that the optical fiber is fixed to the board so that its tip end surface contacts the vertical side surface of the second groove.